Pass integer from view to form in python flask

Question

I have a wtform with a queryselectfield that currently populates with data from the database with all teams:

class PitScoutingForm(FlaskForm):
    team = QuerySelectField(
        query_factory=lambda: Teams.query.all(), get_label='number')

And the view:

@app.route('/competitions/pit-scouting', methods=['GET', 'POST'])
@login_required
def pit_scouting():
    form = PitScoutingForm(request.values)
    form.team.choices = [(a.id, a.number) for a in
                         Teams.query.order_by('number')]

All this works fine. But the team list is growing quite large, and I'd like to limit the teams that show in this field to the currently selected competition, so I'd alter the view to

@app.route('competitions/<int: comp_id>/pit-scouting', methods=['GET', 'POST'])

but I'm not sure how to pass the comp_id from the view to the form so I can filter on the competition id so I only get the teams that are in that competition. I saw this entry but I don't quite understand the solution. Any pointers appreciated.

Answer 1

Thanks for the pointers guys, you led me in a direction that helped. I found another solution that suggested using a plain select field and then loading the choices in init instead like this:

class PitScoutingForm(FlaskForm):
    team = SelectField('Team', coerce=int)
    ...
    def __init__(self, *args, **kwargs):
        super(PitScoutingForm, self).__init__(*args, **kwargs)
        self.team.choices = [(a.id, a.number) for a in Teams.query.order_by('number')]

then my view (ignore the sql...sometimes it's easier than sqlalchemy syntax) remains as is wrt setting the choices, with the exception of using the competition data passed to the view.

@app.route('/pit-scouting/', defaults={'comp': 2}, methods=['GET', 'POST'])
@app.route('/pit-scouting/competitions/<int:comp>', methods=['GET', 'POST'])
@login_required
def pit_scouting(comp):
    sql_text = '''query here'''.format(comp)
    result = db.engine.execute(sql_text)

    form = PitScoutingForm(request.values)
    form.team.choices = [(a.id, a.number) for a in result]

Answer 2

You use the comp_id in your view to only select the teams from that competition. Change comp_id by whatever it's called in your Teams Class.

@app.route('competitions/<int: comp_id>/pit-scouting', methods=['GET',  'POST'])
@login_required
def pit_scouting(comp_id):
    form = PitScoutingForm(request.values)
    form.team.choices = [(a.id, a.number) for a in Teams.query.filter_by(comp_id=comp_id).order_by('number')]

Answer 3

From the Flask Documentation on URL Route Registration:

Variable parts are passed to the view function as keyword arguments.

That means you just need to update your view function to have comp_id as a parameter, like so:

@app.route('competitions/<int: comp_id>/pit-scouting', methods=['GET', 'POST'])
@login_required
def pit_scouting(comp_id):
    form = PitScoutingForm(request.values)
    form.team.choices = [(a.id, a.number) for a in
                     Teams.query.order_by('number')]